Zig-zag dipole antenna



Feb." 13, 1968 R. E. FISK ETAL ZIG-ZAG DIPOLE ANTENNA 2 Sheets-Sheet 2 Filed May 12, 1965 ABOVE NORMAL TO ANTENNA BELOW NORMAL TO A NTENNA llllllllll'lllllllll I0 4- ANGLE 0F DEPRESSION ANGLE 0F ELEVATION INVENTORIS: RONALD E. FlSK,

JOSE PERINI United States Patent Ofltice 3,369,246 Patented F eb. 13, 1968 3,369,246 ZIG-ZAG DIPOLE ANTENNA Ronald E. Fish and Jose Perini, Syracuse, N.Y., assignors to General Electric Company, a corporation of New York Filed May 12, 1965, Ser. No. 455,064 7 Claims. (Cl. 343806) azimuth angle of radiation in the direction of mechanical tilt. It also has been proposed to tilt the main lobe of the radiation pattern from a normal to the antenna by variously feeding or energizing various points of the antenna, for example as described in US. Patent 2,759,183. Not only is the feed of such antenna complex but also the radiation pattern of such an arrangement is highly sensitive to variations in frequency of the radiated energy.

Accordingly, it is an object of the present invention to provide an antenna of the zig-zag type which is of simple construction and which requires but a single point of energization, yet which has a radiation pattern which is asymmetrical with respect to a plane through the center of the antenna over the entire azimuth angle over which it radiates.

It is another object of the present invention to provide a zig-Zag type of antenna in which not only the asymmetry or tilt of the radiation pattern, but also the shape thereof may be easily set as desired particularly with regard to null fill-in of the pattern on the side to which the main lobe is tilted.

It is a further object of the present invention to provide a zig-zag type of antenna with an asymmetrical radiation pattern which retains its contour or form over a relatively broadband of frequencies.

In carrying out the invention in one illustrative embodiment thereof there are provided a pair of zig-zag radiative conductors extending in opposite directions from a common feed or energization region. The elements of the conductors are approximately one-half Wavelength long and are spaced from a reflector which cooperates therewith to radiate energy broadsside therefrom when energized. In accordance with one aspect of the present invention some of the successive elements of one of the radiative conductors remote from the feed region are made progressively shorter than one-half wavelength in small decrements, and corresponding successsive elements of the other of the radiative conductors are made progressively longer than one-half wavelength in correspondingly small increments. Such an arrangement has the effect of progressively advancing the phase of the current from the one radiative conductor and retarding the phasse of the current from the other radiative conductor whereby the resultant radiation from the antenna is asymmetrically distributed with respect to a plane through the center of the antenna.

In accordance with another aspect of the present invention the elements of the radiative conductors adjacent the feed region are made one-half wavelength long in order to maintain the asymmetry of radiation over a relatively broad band of frequencies.

In accordance with a further aspect of the present invention the phase of the current supplied to the one radiative conductor is advanced and the current supplied to the other radiative conductor is retarded in order to provide null fill-in in the minor lobes on the :side of the radiation pattern of the antenna to which the main lobe is tilted. Such a result is accomplished by shortening the ini tial element of the one radiative conductor and lengthening the initial element of the other radiative conductor in relation to a mean length of said initial elements.

The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIGURE 1 is a front view of a zig-Zag panel antenna in accordance with the present invention;

FIGURE 2 is a side view of the antenna of FIGURE 1;

FIGURE 3 is an enlarged view of the center section of the antenna of FIGURE 1 showing the elements thereof adjacent the point or region of energization of the antenna;

FIGURE 4 is a graph showing the relative intensity of radiation from the antenna of FIGURE 1 for angles above and below a normal or a horizontal plane through the center of the antenna; and

FiGURE 5 is a graph in polar coordinates showing the relative intensity of radiation in the horizontal or azimuth direction of the antenna.

Referring now to FIGURES l and 2 there is shown an illustrative embodiment of a zig-zag panel antenna in accordance With the present invention. The antenna comprises a pair of zig-zag radiative conductors 1 and 2 lying in a common plane and extending in opposite directions from a common feed or energization region, at which is located common feed plate 3, and a planar reflective conductor 4 spaced therefrom and in parallel relationship to the plane of conductors 1 and 2. Energization is supplied to the antenna by means of the transmisssion line 5 having an inner conductor 6 connected to the common feed plate 3, and an outer conductor 7 connected to an adjacent point on the reflective conductor. The spacing of the radiative conductors 1 and 2 with resspect to the reflective conductor 4 is such that a current applied to the antenna over the transmission line 5 is substantially radiated outward from the antenna before such current reaches the ends of the radiative conductors 1 and 2.

Theradiative conductor 1 consists of twelve elements, consecutively numbered or ordered 11 through 22, respectively, starting form the comm-on feed plate 3. Similarly the conductor 2 consists of twelve elements, consecutively numbered or ordered 31 through 42, respectively, from the common feed plate 3. The acute angle between adjacent elements of each of the conductors 1 and 2 is conveniently set at about degrees. The con ductors are supported in spaced relationship to the re flector 4 by a plurality of insulators 25 suitably spaced along the length of the conductors. The length L of each of the elements 12 through 16 is one-half wavelength at the frequency of operation of the antenna. The lengths of elements 17 through 22 are progressively shorter than L by a constant decrement AL. The length of D of element 11 of conductor 1 is made appreciably longer than length D-AD of element 31 for reasons to be described hereinafter. Each of elements 32 through 36 are of length L and elements 37 through 42 are made progressively longer than L by a constant increment AL.

Progressively shortening the elements of radiative conductor 1 and progressively lengthening the elements of radiative conductor 2 has the effect of tilting the main lobe of the radiation pattern or the antenna about a normal to the center of the antenna in a direction toward conductor 2. The elements 12 through 16 and 32 through 36 of conductors 1 and 2 provide stability in the contour 3 or form of the radiation pattern over a band of frequencies.

Referring 110W to FIGURE 3 there is shown an enlarged front view of the panel antenna of FIGURES 1 and 2 about the common feed plate 3. In this figure the common feed plate or region is a triangular disc of two apexes of which the adjacent ends of elements 11 and 31 are connected. The length of the conductor 11 is made appreciably greater than the length of conductor 31 to retard the phase of the current supplied to the conductor 1 with respect to the phase of current supplied to conductor 2. The effect of such provisions is to fill in the null regions between the side lobes of the radiation pattern as well as raise the level of the side lobes on the side of the pattern of the antenna panel to which the main lobe is tilted. Such provisions also have the effect of reducing the tilt of the main lobe produced by elements of progressively different length in conductors 1 and 2. The two factors mentioned are set to provide the desired tilt and null fill-in.

As further shown in FIGURE 3 the reflector 4 may be I a wire mesh 26 supported on a plurality of longitudinal members 27, 28, 29, to which the insulators are secured.

The operation of the invention will be more fully described in connection with FIGURE 4 which shows a pair of graphs and 51 of relative field strength versus elevation angle with respect to a normal to the antenna. Graph 50 shows the relative field strength versus elevation angle of radiation to the antenna described in connection with FIGURES 1, 2 and 3. Dotted graph 51 shows a pattern for a similar zig-zag panel antenna except that all of the elements thereof are one-half wavelength at the frequency of operation of the antenna and is shown to illustrate the kind of results attainable by the present invention. It will be noted that the direction of maximum radiation of graph 50 has been shifted downward by approximately 1 degree, and in addition the nulls 52 have been filled-in and the level of the side lobes as shown by 53 raised. The tilt in the direction of the main lobe is produced by the shortened elements of conductor 1 and lengthened elements on conductor 2 as pointed out above. On the antenna on which the pattern of graph 50 was taken, the increment AL was equal to the decrement AL which in turn was made equal to 1/80 L. The conductors 1 and 2 had a cross sectional diameter of 0.02 L. The spacing of the radiative elements from the reflector was about 0.26 L. The indicate-d change in length of the elements of the conductors 1 and 2 remote from the common energization region in the absence of any difference in length of initial conductors 11 and 31 would have produced a tilt of the order of 1 /2 degrees. It order to provide null fill-in on the downward side of the pattern as well as to raise the level thereof the initial elements of the conductors 1 and 2 were made of different lengths, specifically the difference AD in length of the elements 11 and 31 was made one-eighth of a wavelength. The net effeet on the resultant radiation pattern was a reduction in the tilt of the main lobe slightly, a filling in of the nulls on the side of the pattern to which the main lobe was tilted, and a raising of the level thereof. The one-half wave sections 12 through 16, and 32 through 36 provide stability in the pattern as a function of frequency. In this particular antenna the pattern remained relatively constant over a frequency band of better than 3 percent about the frequency of operation of the antenna.

It will be appreciated that the decrements of conductor 1 need not be made equal to the increments of conductor 2. Also the decrement and increment of conductors 1 and 2 could have been made larger than indicated to produce a greater angle tilt of the beam. Also the successive decrements of conductor 1 and successive increments of conductor 2 could have been made progressively larger as desired with the effect of producing a greater degree of tilt. By such provision tilts in the main lobe many times the tilt indicated in the above example could be pro- 4. duced without seriously impairing the general outlines of the radiation pattern. Of course, if desired, to produce a large tilt in the radiation pattern without regard to stability of the pattern over a broad band of frequencies successive elements starting from the common energization region could be made progressively shorter in length, and similarly the elements of conductor 2 starting from the common region of energization could be made progressively longer in length. Such an antenna would be suitable in applications where radiation is confined to a narrow band of frequencies. By expedients such as described above tilts in the main lobe of the order of five degrees have been attained without appreciable change in the resultant radiation pattern.

Of course, if null fill-in is not a particular problem the proportioning of initial elements of conductors 1 and 2 as indicated would not be required. Also, if different degrees of null fill-in are required the differential length AD could be changed from the value indicated. The number of elements of one-half wavelength could be changed as desired, for example they could be decreased where stability with regard to frequency is not required over as broad a band of frequencies.

Referring now to FIGURE 5 there is shown a graph 54 in polar coordinates of the horizontal or azimuth radiation pattern of the antenna of FIGURES 1, 2 and 3 in relative field strength plotted along the radii at various azimuth angles with respect to the direction of maximum radiation.

While the invention has been described and illustrated in connection with a specific example it will be appreci ated that a number of modifications may be made by those skilled in the art without departing from the invention, for example, the angle between the elements in each of the radiative conductors 1 and 2 may be greater or less than 75 degrees. In general'an angle between 60 degrees and degrees provides an adequate horizontally polarized component in the resultant radiation pattern. Also, if desired, the spacing of the radiative conductors from the reflector could be increased thereby enabling a larger amount of energy to be radiated per element thus requiring fewer elements in each of the conductors. While it is desirable that the energization be substantially attenuated at the ends of the radiative conductors in order to avoid reflections therefrom, such is not an absolute requirement. A certain amount of reflection while undesirable would not seriously deteriorate the desired pattern. Accordingly, we intend by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is 1. An antenna comprising:

a pair of conductors each extending in opposite directions from a common region,

each conductor including a plurailty of generally linear elements approximately one-half wavelength long at the frequency of operation of the antenna,

the elements of each of said conductors being serially connected,

even ordered elements of one of said conductors and odd ordered elements of the other of said conductors with reference to said region being oriented in one general direction,

odd ordered elements of said one conductor and said even numbered elements of said other conductor being oriented in another general direction,

a reflector spaced in radiative relationship with said pair of conductors,

a pair of energizing terminals,

means for connecting one of said terminals to the ends of said conductors adjacent said region, and means for connecting the other of said terminals to said reflector,

several successive elements of one of said conductors being progressively shorter than one-half Wavelength,

several corresponding successive elements of said other conductor being progressively longer than one-half wavelength.

2. An antenna comprising:

a pair of conductors each extending in opposite directions from a common region,

each conductor including a plurality of generally linear elements approximately one-half Wavelength long at the frequency of operation of the antenna,

the elements of each of said conductors being serially connected,

even ordered elements of one of said conductors and odd ordered elements of the other of said conductors with reference to said region being oriented in one general direction,

odd ordered elements of said one conductor and said even numbered elements of said other conductor being oriented in another general direction,

a reflector spaced in radiative relationship with said pair of conductors,

a pair of energizing terminals,

means for connetcing one of said terminals to the ends of said conductors adjacent said region, and means for connecting the other of said terminals to said reflector,

several successive elements of one of said conductors being progressively shorter than one-half wavelength,

several corresponding successive elements of said other conductor being progressively longer than one-half wavelength,

the difference in length between successive elements being a small fraction of a wavelength.

3. An antenna comprising:

a pair of conductors each extending in opposite directions from a common region and lying in a common plane,

each conductor including a predetermined plurality of generally linear elements approximately one-half wavelength long at the frequency of operation of the antenna,

the elements of each of said conductors being serially connected,

even ordered elements of one of said conductors and odd ordered elements of theother of said conductors with reference to said region being oriented in one general direction,

odd ordered elements of said one conductor and said even numbered elements of said other conductor being oriented in another general direction,

a reflector spaced in radiative relationship with said pair of conductors,

a pair of energizing terminals,

means for connecting one of said terminals to the ends of said conductors adjacent said region, and means for connecting the other of said terminals to said reflector,

said one conductor including a portion in which successive elements are progressively shorter than onehalf wavelength by a constant decrement,

said other conductor including a corresponding portion in which successive elements are progressively greater than one-half wavelength by a constant increment,

said constant decrement being equal to said constant increment.

4. An antenna comprising:

a pair of conductors each extending in opposite directions from a common region and lying in a common plane,

each conductor including a predetermined plurality of generally linear elements approximately one-haltf wavelength long at the frequency of operation of the antenna,

the elements of each of said conductors being serially connected,

even ordered elements of one of said conductors and odd ordered elements of the other of said conductors with reference to said region being oriented in one general direction,

odd ordered elements of said one conductor and said even numbered elements of said other conductor being oriented in another general direction,

a reflector spaced in radiative relationship with said pair of conductors,

a pair of energizing terminals,

means for connecting one of said terminals to the ends of said conductors adjacent said region, and means for connecting the other of said terminals to said reflector,

said one conductor including a portion in which sucessive elements are progresively shorter than onehalf wavelength by a constant decrement,

said other conductor including a corresponding portion in which successive elements are progressively greater than one-half wavelength by a constant increment,

said constant decrement being equal to said constant increment,

the difference in length between successive elements being a small fraction of a wavelength.

5. An antenna comprising:

a pair of conductors each extending in opposite directions from a common region,

each conductor including a plurality of generally linear elements approximately one-half Wavelength long at the frequency of operation of the antenna,

the elements of each of said conductors being serially connected,

even ordered elements of one of said conductors and odd ordered elements of the other of said conductors with reference to said region being oriented in one general direction,

odd numbered elements of said other conductor being oriented in another general direction,

a reflector spaced in radiative relationship with said pair of conductors,

a pair of energizing terminals,

means for connecting one of said terminals to the ends of said conductors adjacent said region, and means for connecting the other of said terminals to said reflector,

said one conductor including a portion adjacent to said region in which successive elements are one-half wavelength long at the frequency of operation of the antenna, and another portion remote from said region in which successive elements are progressively shorter than one-half wavelength,

said other conductor including a corresponding portion adjacent to said region in which successive elements are one-half wavelength in length and a corresponding remote portion in which successive elements are progressively greater than one-half wave length length.

6. An antenna comprising:

a pair of conductors each extending in opposite directions from a common region,

each conductor including a plurality of generally linear elements approximately one-half Wavelength long at the frequency of operation of the antenna,

the elements of each of said conductors being serially connected,

even ordered elements of one of said conductors and odd ordered elements of the other of said conductors with reference to said region being oriented in one general direction,

odd ordered elements of said one conductor and said even numbered elements of said other conductor being oriented in another general direction,

a reflector spaced in radiative relationship with said pair of conductors,

a pair of energizing terminals,

means for connecting one of said terminals to the ends of said conductors adjacent said region, and means for connecting the other of said terminals to said reflector,

the initial element of said one conductor immediately adjacent to said region having a predetermined length,

a successive first portion of said one conductor including successive elements one-half wavelength in length and a terminal portion in which succesive elements are progressively shorter than one-half wavelength,

the intial element of said other conductor immediately adjacent to said region being appreciably shorter than the initial elementof said other conductor,

a successive first portion of said conductor including successive elements one-half wavelength in length and a terminal portion in which successive elements are progressively longer than one-half Wavelength.

7. An antenna comprising:

a pair of conductors each extending in opposite directions from a common region,

each conductor including a plurality of generally linear elements approximately one-half Wavelength long at the frequency of operation of the antenna,

the elements of each of said conductors being serially connected,

even ordered elements of one of said conductors and odd ordered elements of the other of said conductors with reference to said region being oriented in one general direction,

odd ordered elements of said one conductor and said even numbered elements of said other conductor being oriented in another general direction,

a reflector spaced in radiative relationship with said pair of conductors,

a pair of energizing terminals,

means for connecting one of said terminals to the ends of said conductors adjacent said region, and means for connecting the other of said terminals to said reflector,

the initial element of said one conductor immediately adjacent to said region having a predetermined length,

a successive first portion of said one conductor including successive elements one-half Wavelength in length and a terminal portion in which successive elements are progressively shorter than one-half wavelength,

the initial element of said other conductor immediately adjacent to said region being appreciably shorter than the initial element of said other conductor,

a successive first portion of said conductor including successive elements one-half Wavelength in length and a terminal portion in which successive elements are progressively longer than one-half wavelength,

the diiference in lengths of said initial conductors being about an order of magnitude greater than the difference in length of said successive elements of said conductors.

References Cited UNITED STATES PATENTS 2,759,183 8/1956 Woodward 343806 HERMAN KARL SAALBACH, Primary Examiner.

M. L. NUSSBAUM, Assistant Examiner. 

1. AN ANTENNA COMPRISING: A PAIR OF CONDUCTORS EACH EXTENDING IN OPPOSITE DIRECTIONS FROM A COMMON REGION, EACH CONDUCTOR INCLUDING A PLURALITY OF GENERALLY LINEAR ELEMENTS APPROXIMATELY ONE-HALF WAVELENGTH LONG AT THE FREQUENCY OF OPERATION OF THE ANTENNA, THE ELEMENTS OF EACH OF SAID CONDUCTORS BEING SERIALLY CONNECTED, EVEN ORDERED ELEMENTS OF ONE OF SAID CONDUCTORS AND ODD ORDERED ELEMENTS OF THE OTHER OF SAID CONDUCTORS WITH REFERENCE TO SAID REGION BEING ORIENTED IN ONE GENERAL DIRECTION, ODD ORDERED ELEMENTS OF SAID ONE CONDUCTOR AND SAID EVEN NUMBERED ELEMENTS OF SAID OTHER CONDUCTOR BEING ORIENTED IN ANOTHER GENERAL DIRECTION, A REFLECTOR SPACED IN RADIATIVE RELATIONSHIP WITH SAID PAIR OF CONDUCTORS, 